Magnetic anchor for curved and irregular surfaces



Feb. 24, 1970 K. H. KELLER 3,497,846

MAGNETIC ANCHOR FOR CURVED AND IRREGULAR SURFACES Filed Dec. 27, 1968 2 Sheets-Sheet 1 INVENTOR KARL H. KELLER ATTORNEY Feb. 24, 1970 K. H. KELLER 3,

MAGNETIC ANCHOR FOR CURVED AND IRREGULAR SURFACES Filed Dec. 2'7, 1968 2 Sheets-Sheet 2 INVENTOR mm. H. KELLER ATTORNEY United States Patent 3,497,846 MAGNETIC ANCHOR FOR CURVED AND IRREGULAR SURFACES Karl H. Keller, Arnold, Md., assignor to the United States of America as represented by the Secretary of the Navy Filed Dec. 27, 1967, Ser. No. 693,806 Int. Cl. H01f 1/28 U.S. Cl. 335296 8 Claims ABSTRACT OF DISCLOSURE The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This present invention relates to an improvement in lifting magnets. The present invention provides reduced reluctance paths for a lifting magnet when lifting ferromagnetic objects having curved or irregular surfaces by providing on the poles of the magnet facing means which is capable of adapting to irregular or curved configurations of the object to be lifted.

In the prior art structure of lifting magnets the face of the magnet has usually been made of a rigid ferromagnetic material such as iron and has been designed as a planar surface. Such surfaces are poorly adapted to engage and lift curved surfaces since the area of contact i small and the lifting force is proportional to this area of contact, that is, for a magnet of a given power the lifting force is greater for a greater area of contact.

It is an object of this invention to provide greater holding capacity for a lifting magnet when lifting objects having curved or irregular surfaces.

Another object of this invention is to provide a lifting magnet of reduced weight for a given lifting power.

A further object of the present invention is to provide a lifting magnet having improved holding power at angles less than normal to the surface.

There is shown in FIGURE 1 a perspective view par tially cut away.

FIGURE 2 is a diagrammatic view of the invention applied to a magnet with associated electrical circuitry.

Referring now to the drawing there is shown by way ofillustration at 10 a lifting magnet which may be of the electromagnet type or of the permanent magnet type or of the ceramic magnet type. For simplicity the invention will be described in its application to an electromagnet. Each of the pole pieces 14 and 15 has attached thereto a flexible thin walled container or bag 11 made of' any suitable material such as plastics or leather. These bags may be attached to the face of the magnet pole pieces in any suitable manner, as by cement, clamping, etc. Contained within each of the bags 11 are powders or small particles 12 of a suitable ferromagnetic material such as soft iron. These particles 12 may be suspended in a suitable fluid such as oil or grease, or the particles might be suspended in a suitably pliable elastomer. In simple form, the electrical circuit as shown in FIG. 2 consists of a magnetizing winding 16 connected through 3,497,846 Patented Feb. 24, 1970 a rheostat 17 for controlling the level of magnetization and a double pole double throw reversing switch 18 for selecting the direction of magnetization to a battery 19.

In operation the electromagnet 10 is applied to the surface of a ferromagnetic object 13 in an unenergized condition so that the particles 12 in the bags 11 are unmagnetized and can adjust to the shape of the object 13. When the magnet is energized by closing switch 18 the particles, as is well known in magnetic clutches, form a firm linkage between the face of the magnet and the object so the magnetic reluctance of the magnetic path is low, much lower than with a fiat faced magnet applied to a curved surface where, the area of contact is reduced to substantially a line contact and may contact only two of the poles.

When the principle of this invention is applied to a permanent magnet, means must be provided to remove the magnetic particles from the magnetic field until the face of the magnet adjusts to and mates with the configuration of the surface to be held by the magnet. In some instances this could be accomplished by providing a magnetic shunt 21, as shown in FIG. 2 in broken lines, or by introducing an air gap between the magnet and bag. Another method of controlling the field of a permanent magnet would be to provide a winding, such as 16 in FIG. 2, then by closing switch 18 in the proper direction a field which would tend to neutralize the field of the permanent magnet may be produced. In the case of ceramic magnets, there is known a technique for con trolling the magnetic condition of the magnet which utilize a pulsed current. That is to say that with at least some ceramic magnets the material has the property that when a magnetic field is applied to the material, as by a pulsed current flow in a winding such as 16 in FIG. 2, the material becomes magnetized in one direction and after the duration of the pulse acts as a permanent magnet. Such a magnet can then be demagnetized by a similar pulse flowing in the opposite direction in the magnetizing winding 16.

The intimate contact between the magnet face and the object has the advantage of resisting both normal and horizontal displacement of the magnet. It may be noted that the principle of the present invention is applicable to many conventional forms of magnetic holding devices in addition to lifting magnets, e.g. hold-downs, magnetic chucks, magnetic valves and pumps.

It is to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described herein.

What is claimed is:

1 An improvement in magnetic holding devices comprising:

a body of magnetic material having a plurality of pole p1eces;

a plurality of flexible containers attached one to each pole piece face of the magnet; and

a quantity of magnetizable particles contained in suspension within each of said containers,

whereby, upon provision of a magnetized condition of said magnetic material said particles are magnetized to provide a flux path to an object to afford adherance of said object to said device.

2. A device as claimed in claim 1 in which the magnet is an electro magnet.

3. A device as claimed in claim 1 in which said magnet is a permanent magnet further comprising:

means for interrupting the magnetic field to permit said containers to adjust to the configuration of the surface to which said magnet is applied.

4. A device as claimed in claim 1 in which said particles are powdered ferromagnetic material in suspension.

5. A device as claimed in claim 4 in which said ferromagnetic material is suspended in an oil.

6. A device as claimed in claim 4 in which said ferr0- magnetic material is suspended in a grease.

7. A device as claimed in claim 4 in which said ferromagnetic material is suspended in an elastomer.

8. A device as claimed in claim 1 in which the magnet is composed of magnetic material having the prop erty of being magnetized responsive to application of pulse energy thereto, and demagnetized responsive to subsequent pulse energy applied thereto.

References Cited UNITED STATES PATENTS 10 G. HARRIS, Primary Examiner D. M. MORGAN, Assistant Examiner US. Cl. X.R. 

